GPS instead of turn and bank

Newps writes:

So now you're changing the subject? Good one.

No. I'm trying to illustrate, in multiple ways, why a GPS receiver
alone cannot serve to measure banking or turning.

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Newps writes:

All you care about is that you're actually turning. Or not turning.
The GPS does very well at that.

No, it does not. The GPS knows only your ground track. Nothing else.
If you are flying straight and level, and the wind changes, your
ground track may show a turn, even though you haven't turned in the
air. If you turn as the wind changes, your ground track may show no
change, even though you are turning and banking in the wind.

Thus, a GPS alone cannot serve as a turn and bank indicator. QED.

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Nomen Nescio writes:

Well, just for s**ts & grins, I just did a flight on MSFS....In IMC........1000ft
ceiling, where I took off, climbed to 3000 ft, flew over another airport (20nm
away), turned around, flew back, and landed at the same airport. I did
this using NOTHING but the altimeter and GPS. It wasn't pretty......but I did it.
Oh, and I enabled the "real weather" option....kinda windy here in the NE, today.

All well and good ... but how did you determine your bank angle and
rate of turn with the GPS?

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writes:

A few years ago I wrote my own Flight Management software. It
contains obvious things like a moving map, nearest airports etc. , but
it also contained a GPS derived attitude indicator. As has been
suggested here earlier, the GPS gives me lon, lat and hopefully
altitude. My program then actually calculates the rate of ascent/
descent and left/right turn. This coupled with the ground speed gives
you enough information to deduce what the horizon would look like.
Now it makes of course some assumptions, like that the turn is
coordinated, this can be easily verified by the slip/skid ball, which
BTW has a fairly high MTBF.

How do you know and allow for the wind speed?

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Mxsmanic wrote:
Newps writes:


So now you're changing the subject? Good one.


No. I'm trying to illustrate, in multiple ways, why a GPS receiver
alone cannot serve to measure banking or turning.




And you fail utterly. As usual.

Mxsmanic wrote:

Newps writes:


All you care about is that you're actually turning. Or not turning.
The GPS does very well at that.


No, it does not. The GPS knows only your ground track. Nothing else.


Nothing else is needed, as has been pointed out before. If you had any
actual flying experience you would know the wind is irrelevant. Even
flying thru a front is irrelevant.



If you are flying straight and level, and the wind changes, your
ground track may show a turn, even though you haven't turned in the
air. If you turn as the wind changes, your ground track may show no
change, even though you are turning and banking in the wind.

Not relevant in the real world.

On Feb 5, 3:10 pm, Mxsmanic wrote:
writes:
How do you know and allow for the wind speed?

For real practical purposes it really does not matter a lot. Note
that I am interested in the RATE of turn. Of course if the wind
direction and speed changes every second by a very large amount you
may have false "temporary attitudes", now that would constitute pretty
severe turbulence and wind sheer I would imagine. I can go through my
calculations but as I recall a standard rate turn 3 degrees /second
turn at 120kts will yield a 17 degree horizon (coordinated) I think.

An example:Let's say that my magnetic compass shows due North (Mag
Var = 0) I am going at 100kts TAS wind is 10kts from the west 270.
This means that my ground track is appr 006 Magnetic. I don't care,
what I care about is that the rate of change to my ground track (first
derivative) is the same when I do a left coordinated bank versus a
right coordinated turn, obviously my ground track profile will be
different but I don't care, I am not doing turns around a point.
That's the premise and it seems to work fairly reasonably well,
believe me if everything else failed ...

Newps writes:

And you fail utterly. As usual.

In any communication system, failures can occur at either the
transmitting or the receiving ends.

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Newps writes:

Nothing else is needed, as has been pointed out before. If you had any
actual flying experience you would know the wind is irrelevant. Even
flying thru a front is irrelevant.

Explain how you distinguish between wind changes and turns by looking
at a ground track alone.

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Mxsmanic wrote:

Newps writes:


Nothing else is needed, as has been pointed out before. If you had any
actual flying experience you would know the wind is irrelevant. Even
flying thru a front is irrelevant.


Explain how you distinguish between wind changes and turns by looking
at a ground track alone.

What we're trying to do here is keep the plane flying safely straight
and level after the loss of certain instruments. Altitude is much less
important than right/left. As long as the GPS is steady on a ground
track I'm safely upright. No amount of crosswind or frontal passage
wind shift will alter that. I may in fact be in a very slight bank to
maintain a ground track, doesn't matter as it on the order of a degree
or less. So I don't care what the drift is, the primary importance is
keeping the plane upright. I'll also eliminate drift by selecting a
waypoint to go to. Stay on the line drawn by the GPS and the heading is
irrelevant. I hand fly hundreds of miles on cross countries without
getting more than a tenth of a mile off the straight line between the
two points. All this and never looking at the heading indicator. Don't
need it, just look at the line.